Clinical Significance: 
Recently established guidelines from the American Society for Clinical Pathology (ASCP), College of American Pathologists (CAP), Association for Molecular Pathology (AMP), and/or the American Society of Clinical Oncology (ASCP) recommend HER2 testing in invasive breast cancer patients.

https://www.nccn.org/professionals/physician_gls/pdf/breast.pdf

Specimen Requirements and Collection:
Formalin fixed tissue containing a sufficient amount of tumor (generally at least several mm of tumor tissue submitted in the tissue block). 

Methodology:
Fluorescent in-situ hybridization (FISH) dual-probe assay

Forms:
Molecular pathology requisition form

Transport:
Send formalin-fixed, paraffin-embedded (FFPE) tissue and cell block containing tumor at room temperature.  Also acceptable 2-unstained, 4-5 micron positively charged slides with 1 post H&E.  Please include a surgical pathology report

Unacceptable specimen:
Specimens fixed in alternative fixatives or metal fixatives (ex. B-plus).  Decalcified specimens.

Reference Range:
Group 1 HER2/CEP17 ratio >= 2.0 and Avg. HER2 CN >= 4.0 = PRESENT = POSITIVE
Group 2 HER2/CEP17 ratio >= 2.0 and Avg. HER2 CN < 4.0 = IHC REFLEX
Group 3 HER2/CEP17 ratio < 2.0 and Avg. HER2 CN >= 6.0 = IHC REFLEX
Group 4 HER2/CEP17 ratio < 2.0 and Avg. HER2 CN >=4.0 and < 6.0 = IHC REFLEX
Group 5 HER2/CEP17 ratio < 2.0 and Avg. HER2 CN <4.0 = ABSENT = NEGATIVE
NOTE:  IHC REFLEX is recommendation for immunohistochemistry to further clarify the FISH results.

https://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2018-0902-SA

CPT codes:
88377

Test reported:
Results are reported within 7-10 days